if there is already a label set in a category by user, don't double/additionally set one

[felixhaeberle]

Problem

Maige double (additonal) sets labels in the same "category", if user has already selected one.

Solution

If there is already a label set in a category by user, don't double / additionally set one. Only allow double setting in one category if no label was chosen initially.

[maige-app]

@tedspare, this issue has been labeled as both a bug and an enhancement. It seems to involve a UI behavior regarding label management, which might require your attention. Please review and advise on the next steps.

_{From Maige. How's my driving?}